7

LT1793

CC

HARA TERISTICS

A

TYPICALPERFOR

CE

Short-Circuit Output Current

vs Temperature

TEMPERATURE (

°C)

–75

10

15

20

25

30

–25

50

25

100

1793 G19

35

40

–50

0

75

125

SINK

SOURCE

Supply Current vs Temperature

TEMPERATURE (

°C)

–75

3

4

–25

50

25

100

1793 G20

5

–50

0

75

125

S

APPLICATI

I FOR ATIO

LT1793 vs the Competition

With improved noise performance, the LT1793 in the

PDIP directly replaces such JFET op amps as the OPA111

and the AD645. The combination of low current and

voltage noise of the LT1793 allows it to surpass most dual

and single JFET op amps. The LT1793 can replace many

of the lowest noise bipolar amps that are used in amplify-

ing low level signals from high impedance transducers.

The best bipolar op amps (with higher current noise) will

eventually lose out to the LT1793 when transducer im-

pedance increases.

Figure 1. Comparison of LT1793, OP215, and AD822

Input Bias Current vs Common Mode Range

COMMON MODE RANGE (V)

–15

–100

–60

–40

–20

0

20

40

–10

–5

05

1793 F01

10

60

80

100

–80

15

LT1793

AD822

CURRENT NOISE =

OP215

TEMPERATURE (

°C)

0

300p

100p

3n

1n

30n

10n

100

1793 G21

30p

10p

3p

1p

0.3p

25

50

75

125

BIAS

CURRENT

OFFSET

CURRENT

Input Bias and Offset Currents

vs Chip Temperature

Ω) assures that

the input bias current is almost constant over the entire

common mode range. Figure 1 shows how the LT1793

stands up to the competition. Unlike the competition, as the

input voltage is swept across the entire common mode

range the input bias current of the LT1793 hardly changes.

As a result the current noise does not degrade. This makes

the LT1793 the best choice in applications where an

amplifier has to buffer signals from a high impedance

transducer.

Offset nulling will be compatible with these devices with the

wiper of the potentiometer tied to the negative supply

(Figure 2a). No appreciable change in offset voltage drift

2

3

1

5

50k

15V

– 15V

4

6

7

2

3

1

5

50k

10k

10k

15V

– 15V

(b)

(a)

1793 F02

4

6

7

Figure 2